Memotech Bill
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Re: My own Retro homecomputer called RhoCoCo

Fri Nov 23, 2018 1:00 pm

Gavinmc42 wrote:How old does the Pi have to be before it is retro?
When it has a 26 pin header?
Or when 128 bit CPUs and PetaByte RAM are the norm?
Gavinmc42 wrote:Gert has done VGA, perhaps use a Zero as a VDP/6845 emulator?
Thought about exactly that, using a Zero running bare metal as a display generator for a Memotech. But seemed a bit pointless since a Zero can emulate the entire Memotech http://www.primrosebank.net/computers/r ... memupi.htm. Rather like the days when the LaserJet printer had a much more powerful CPU than the DOS machine printing to it.
Gavinmc42 wrote:Most of us who can remember these old CPU's are getting a bit Retro ourselves
True. I even consider sub-contracting PCB manufacture to be cheating :)
Last edited by Memotech Bill on Fri Nov 23, 2018 2:10 pm, edited 1 time in total.

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mahjongg
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Re: My own Retro homecomputer called RhoCoCo

Fri Nov 23, 2018 1:26 pm

Gavinmc42 wrote:
Fri Nov 23, 2018 10:28 am
Are 22LV10's still available?
I won't use GAL's for my designs, as the task of programming them is a barrier for anyone trying to build a rhococo, and its also a "black box" and if you loose the knowledge of how they are programmed you are stuck replicating one.

But yeah, GAL's like that are still available.

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Re: My own Retro homecomputer called RhoCoCo

Fri Nov 23, 2018 5:13 pm

Gavinmc42 wrote:
Fri Nov 23, 2018 10:28 am
How old does the Pi have to be before it is retro?
I consulted the Unicorns. When the Pi4 comes out, any Pi that isn't directly compatible will be retro.
But they claimed that NDAs prevent them from revealing which Pis wn't be compatible.
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DavidS
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Re: My own Retro homecomputer called RhoCoCo

Fri Nov 23, 2018 6:09 pm

davidcoton wrote:
Fri Nov 23, 2018 5:13 pm
Gavinmc42 wrote:
Fri Nov 23, 2018 10:28 am
How old does the Pi have to be before it is retro?
I consulted the Unicorns. When the Pi4 comes out, any Pi that isn't directly compatible will be retro.
But they claimed that NDAs prevent them from revealing which Pis wn't be compatible.
Strange, as the Raspberry Pi has been a series of mostly compatible systems. The only real compatibility issues being releated to addresses moving to allow more memory, and the adition of hypervisor mode on the ARMv7/v8 based RPi's. I am using even the same exact page table implementations for the BCM2835 and BCM2837 based RPi's, that is extremely compatible.

Ok there is the loss of the SWI instruction with the ARMv8 that has caused some compatibility issues, though not much.

I did not think that anything was going to be changed that would really break compatibility.
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Re: My own Retro homecomputer called RhoCoCo

Fri Nov 23, 2018 6:12 pm

mahjongg wrote:
Fri Nov 23, 2018 1:26 pm
Gavinmc42 wrote:
Fri Nov 23, 2018 10:28 am
Are 22LV10's still available?
I won't use GAL's for my designs, as the task of programming them is a barrier for anyone trying to build a rhococo, and its also a "black box" and if you loose the knowledge of how they are programmed you are stuck replicating one.

But yeah, GAL's like that are still available.
We have all been using GAL's to do things with computer hardware since the early 1980's, so I do not think there is much of a risk of it being seen as a black box, or of the knowledge being lost.
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mahjongg
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Re: My own Retro homecomputer called RhoCoCo

Fri Nov 23, 2018 6:27 pm

Been there, done that, could not build a copy of a design because I could not find out what was in the PAL. Sometimes engineers simply forget to document such things.

Forcing someone who wants to build a rhococo (clone) to program a PAL/GAL isn't pleasant.

GALs and PALs may be comfortable to use, but that comfort isn't worth it, if you want to create a system that can be easily replicated.

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Re: My own Retro homecomputer called RhoCoCo

Fri Nov 23, 2018 8:16 pm

DaveS,
We have all been using GAL's to do things with computer hardware since the early 1980's, so I do not think there is much of a risk of it being seen as a black box, or of the knowledge being lost.
Yes, but there are few problems with the use of GALs/PALs and the like in a design like this:

1) Anyone wanting to build one needs a programmer to configure them. That is a no-no.

2) Then they need the software application to create the configuration and program them. That is a no-no.

3) The they probably need MS-DOS to run that application on. That is a no-no.

4) Or they need to rely on being able to get pre-programmed devices from the designer or elsewhere. That is not sustainable.

5) They are indeed black boxes compared to using standard logic chips for which data sheets are readily available.

6) They are also "black boxes" in the way that anyone becoming familiar with old skool logic devices might be totally put off by GALs/PALs.

All in all I think mahjongg is right. Stick to "jelly bean" parts.

As it happens I have just salvaged a couple of 8088 based embedded system boards. 1980's vintage. Full of good old 1980's RAMS, ROMs, timers, UARTs, TTL glue logic, etc. I'm intent on getting them working but sure enough they have a bunch of PALs on board and I have no way to know what they are doing. I'll figure it out but it's a pain.

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Re: My own Retro homecomputer called RhoCoCo

Sat Nov 24, 2018 7:25 am

How old does the Pi have to be before it is retro?

When it has a 26 pin header?
Hey I have a bunch of those, I'm Pi retro? :lol:

I have used Flashrom and OpenOCD on Pi's.
Not sure if they do GALs? And if PAL/?GALs are not retro then that line is drawn real early.
Most CPLDs are big these days or tiny BGA packages, any DIPs still around?
True. I even consider sub-contracting PCB manufacture to be cheating :)
Yep just like subcontracting PCB track routing to companies who had 386+387 or 486 PC's with the latest Neural routing software.
Or getting PCB artwork made by companies with cameras you can walk inside.
Or making that Artwork with Bishop tape in the latest fancy red and blue tapes.
How about a wire wrap version, manual or fancy motor wrapper?
Wire wrap is great, you can make small PCBs with many layers of wire.
Most of my prototypes had normal IC sockets with soldered wire wrap wire.
8 layer boards no problem, the fast ones only had 4MHz clocks ;)

Only 5 Volts is Retro? 3V3 need not apply?

Microchip still have 22V10 etc.
Ouch, VHDL design and programming them, I had forgotten that part.
Ok, now that is Retro, my first VHDL designs were done on paper.
Perhaps I can used a PSoC 1 in a 28pin dip to emulate a 22V10?

How many gates are needed for a 6845?
http://www.microvga.com/#

Pi zero as graphics card ;) https://rc2014.co.uk/
https://www.youtube.com/watch?v=wVUlORo0-Ak
Ok, it's official, I'm old, I knew every reference in that conversation.
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Re: My own Retro homecomputer called RhoCoCo

Sat Nov 24, 2018 9:10 pm

If programmable logic chips were simply 'purchase and install on the board', were programmed / configured by the system itself on start-up, I would not have a problem with using them in a project designed to be built by others.

When they need to be programmed before installation, need a programmer building to do that, it's a lot less appealing, it becomes another obstacle to participation.

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Re: My own Retro homecomputer called RhoCoCo

Sun Nov 25, 2018 7:31 am

Yep. If you're going to put a programmable device on their and impose all that hassle on any potential builder of the board you might as well go the whole hog and put the whole design into an FPGA. Smaller, cheaper, faster. But that kind of misses the whole point of the project.
Last edited by Heater on Sun Nov 25, 2018 5:32 pm, edited 1 time in total.

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Re: My own Retro homecomputer called RhoCoCo

Sun Nov 25, 2018 4:38 pm

hippy wrote:
Sat Nov 24, 2018 9:10 pm
When they need to be programmed before installation, need a programmer building to do that, it's a lot less appealing, it becomes another obstacle to participation.
Though in the Retrobrew community, since the board designer is usually the supplier of the boards, any GALs, EPROMs, Flash or Propellers are usually programmed and supplied as an option with the board. It's not a huge barrier, and is appreciated by folks like me who don't have every programmer under the sun.
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Re: My own Retro homecomputer called RhoCoCo

Sun Nov 25, 2018 5:53 pm

scruss,

I have no idea what goes on in the "Retrobrew community", which sounds great by the way, but a big thing now a days is open source hardware.

That is to say the designer publishes his schematics, board layout files, bill of materials, source code for ROMs etc. Such that anyone can buy the components and make the board how they like. With no dependence on the original designer for supplies of anything. See Arduino for example.

Of course getting ROMs programmed is a bit of a hurdle.

PALs and such are a much bigger hurdle. Better not to go there if you want people to use your creations.

As you say "...appreciated by folks like me who don't have every programmer under the sun."

Especially appreciated by anyone that wants to recreate the thing long after the designer has lost interest or otherwise disappeared.

Oh wait, I am part of the "Retrobrew" community it seems. Here is my Z80 emulator on a Parallax Propeller running CP/M https://hackaday.com/2009/12/27/zilog-in-a-matchbox/

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Re: My own Retro homecomputer called RhoCoCo

Sun Nov 25, 2018 7:51 pm

One way to avoid having to need to use an EEPROM Programmer to program/re-program the EEPROM is to replace the EEPROM with a CMOS Flash memory chip such as the Atmel AT29C256 or similar.

Requires a minor modification by connecting the processor write signal to the flash memory and then the CMOS Flash can be re-written without the need for a programmer.

I designed a board using a Z8180 many years ago, ~1985. I still very occasionally use it and I am able to update the code if needed without needing a programmer. I connect the board's serial port to a PC, issue a command to the board to interrupt the operating code and enter a simple monitor and one of the routines in the monitor allows me to rewrite the Flash memory by downloading the new code via the serial port.

Just one possible issue is if these types of devices are still available, but it certainly makes rewriting code far easier.
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Re: My own Retro homecomputer called RhoCoCo

Mon Nov 26, 2018 12:55 am

PAL and GALs seem to have gone like the Dodo.
Closest DIp package still available from Digikey is the ATF750 which is a superset of the 22V10.

PALs and GALS are Retro, remember Palasm?
https://en.wikipedia.org/wiki/PALASM

Pi's make great hacking gadgets, programs like Flashrom and OpenOCD work on Raspbian.
https://www.flashrom.org/Flashrom
http://openocd.org/

I am assuming anyone of this Forum has a Pi and could use their Pi to program chips.
May need a logic level converter for 5V PLDs + 15V programming voltage generator?
PLDs make memory bank switching easier?
Could you make your own CPU from CPLD? Intel 4004?
http://www.fpgacpu.org/links.html

I suppose once you have programmed a PLD, CPLDs look like the next step, then FPGA's?
Once you have done FPGA, roll your own RISC-V?
If all that is not learning, perhaps another hobby?
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Re: My own Retro homecomputer called RhoCoCo

Mon Nov 26, 2018 3:10 am

Heater wrote:
Sun Nov 25, 2018 5:53 pm
I have no idea what goes on in the "Retrobrew community", which sounds great by the way, but a big thing now a days is open source hardware.
I know. And some of the open source designs use GALs, esp. if they're based on an older design. Like the SBC6120-RBC I'm building. The only reason the board (re)designer is supplying chips is because the CPUs are fiendishly hard to get, and sometimes you get a chip that isn't an HD-6120.
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Re: My own Retro homecomputer called RhoCoCo

Mon Nov 26, 2018 8:05 am

Gavinmc42,
Once you have done FPGA, roll your own RISC-V?
I'm already on it.

A year or so ago I decided it was time to get familiar with FPGA and Verilog. So I ended up taking Clifford Wolf's picorv32 RISC V Verilog core and wrapping it around with my own attempt at making peripiperals in Verilog, UART, GPIO... Works a treat: https://github.com/ZiCog/xoro

Then, getting ambitious, I decided I need to design my own RISC V core from scratch. In the mean time I discovered a much nicer hardware description language, SpinalHDL, http://spinalhdl.github.io/SpinalDoc/. The result so far is a mostly complete and tested, but as yet not running, RISC V core https://github.com/ZiCog/sodor-spinal

What prompted me to get into this Verilog world is that there are now Open Source tools to take your Verilog all the way from source to FPGA bit stream. No more dependence on the big ugly IDE's from the FPGA vendors. You can program FPGA's from your Raspberry Pi !
See here: http://www.clifford.at/yosys/

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Re: My own Retro homecomputer called RhoCoCo

Mon Nov 26, 2018 8:23 am

scruss,

Wow, the SBC6120-RBC is a wonderful project. I didn't even know there was such a thing as a Harris HD-6120 CMOS “PDP-8 on a chip”.

Given that the HD-6120 is pretty much "unobtainium" I can forgive the uses of PALs. This is quite a specialist project.

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Re: My own Retro homecomputer called RhoCoCo

Mon Nov 26, 2018 12:07 pm

The biggest socketable chips I ever used were the 84pin PLCC MC68HC11K4.
PLCC chips and sockets are prototype breadboardable, ie no Chinese made PCB needed, 0.1" vero type pcb is ok.
84pin PLCC CPLD are still available, what can be made with an ATF1508 CPLD?
VGA driver can be done?
A 44pin PLCC CPLD would do most of the RhoCoCo logic?

Thanks Heater, FPGA getting doable without $$$ tools?
That SpinalHDL looks interesting - AXI in a single line :D
VexRISC-V and VGA?
So little time, so much still to learn.
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Re: My own Retro homecomputer called RhoCoCo

Mon Nov 26, 2018 12:54 pm

The FPGA tools from the likes of Altera (Now Intel) and Xilinx have been free for use for many years. At least for the lower end FPGA.

By beef with them, what put me off toying with FPGA for fun in the past, is that they are huge, slow, clumsy and complex to use.

Now we have the likes of Yosys and really cheap FPGA's like the Lattice parts that Yosys supports. Which all coincides with the arrival of RISC V. Wonderful.

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Re: My own Retro homecomputer called RhoCoCo

Mon Nov 26, 2018 1:25 pm

Gavinmc42 wrote:
Mon Nov 26, 2018 12:55 am
I suppose once you have programmed a PLD, CPLDs look like the next step, then FPGA's?
Once you have done FPGA, roll your own RISC-V?
I would suggest skipping PLD and CPLD and going straight to FPGA. FPGA are much easier to interface to and therefore to program and use and there's not really a lot to be gained from starting with anything else. RISC-V would be a good goal once one has the basics of using an FPGA and the programming software grasped.

Now the Foundation are moving into Value Added Revenue Generating Add-Ons like the PoE HAT and the DVB TV Tuner I'm hoping there may be something like a cheap Foundation FPGA HAT in the pipeline.

There are third-party FPGA products but something with Foundation support and a community all working around a common platform would I think give FPGA development with a Pi a real kick. The Gnarly Grey UPDuino boards are probably a good option for starting out -

http://www.gnarlygrey.com

I just wish I had more time to do the things I would like to do.

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Re: My own Retro homecomputer called RhoCoCo

Mon Nov 26, 2018 3:25 pm

Heater wrote:
Mon Nov 26, 2018 8:23 am
Harris HD-6120 CMOS “PDP-8 on a chip”. …
Used in the DECMate and the companion operator console for some of the later/bigger PDP-11s. It's apparently a little slower than a PDP-8/E, and I know I could have gone for a PiDP-8/I , but this is interesting hardware.

On your FPGA interests, you should chat with Chris Tyler at the Seneca Centre for Development of Open Technology (CDOT). Chris is one of the very early Raspberry Pi developers and is now working on making FPGA development more available.
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Re: My own Retro homecomputer called RhoCoCo

Mon Nov 26, 2018 4:49 pm

scruss wrote:
Mon Nov 26, 2018 3:25 pm
Heater wrote:
Mon Nov 26, 2018 8:23 am
Harris HD-6120 CMOS “PDP-8 on a chip”. …
Used in the DECMate and the companion operator console for some of the later/bigger PDP-11s.
I remember one of the electronics magazines having a project using its fore-runner, the Intersil IM6100. Happy memories of wishing to build projects I couldn't afford as a kid. I was in awe of Nat-Semi's PACE and "16-bits". At the other extreme I still desire a Motorola MC14500B ICU, effectively a 1-bit micro.

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Re: My own Retro homecomputer called RhoCoCo

Mon Nov 26, 2018 5:51 pm

scruss,
...you should chat with Chris Tyler at the Seneca Centre...
I'm not sure I have anything very clever to offer to those guys.
...is now working on making FPGA development more available.
Except...

We now have Open Source FPGA development tool chains. Yosys being the pioneer here for some Lattice devices. Clifford Wolf and friends are expanding that to other devices now.

We now have SpinalHDL which makes describing hardware designs a lot easier and nicer than Verilog or VHDL.

If we consider all of this to be like the GCC C/C++ compiler for FPGA then what it needs to make it accessible to the masses is something like what the Arduino IDE did for C++ on the AVR chips.

A small, cheap, Open Source FPGA board plus a drop dead easy HDL IDE would be a nice project for Seneca.

Just a thought...

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Re: My own Retro homecomputer called RhoCoCo

Mon Nov 26, 2018 8:10 pm

hippy wrote:
Mon Nov 26, 2018 4:49 pm
At the other extreme I still desire a Motorola MC14500B ICU, effectively a 1-bit micro.
So, like one of these? RetroBrew Computers Forum: General Discussion » Mini MC14500 board
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Gavinmc42
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Re: My own Retro homecomputer called RhoCoCo

Tue Nov 27, 2018 12:29 am

How many MC14500s can fit in a lattice fpga?
I am going to have to stopping reading this thread, it's giving me too many ideas.

Does that MC145000 remind anyone of the VC4 QPUs?
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